Electric contact



Feb. 27, 1934. R. swlNN ELECTRIC CONTACTv Filed JulyV 21, 1932 INVENTOR/P/araSa//lfz/Ye.

ATToR EY Patented Feb. 21, 1934 PATENT OFFICE ELECTRIC CONTACT` RichardSwinne, Berlin-Siemensstadt, Germany,

assignor to Westinghouse Electric & Manufacturing Company, Pittsburgh,Pa., a corporation of Pennsylvania.

Application July 21, 1932, Serial No. 623,825 In qermany July 29, 1931 9Claims.

My invention relates to electrical contacts and to contacts arranged tointerrupt current flow in an electric circuit.

I have discovered that contacts at least one of 5 which consists of theelement gallium are remarkable for extremely low contact resistance.

One object of my invention is accordingly, to produce a contact betweendifferent parts of an electrical circuit by providing separable contactsbetween two masses of gallium (or gallium alloy), or between a gallium(or gallium alloys) contact and a contact of copper, mercury, tungsten,nickel or other metal.

Another object of my invention is to provide an electrical switch inwhich one or both separable contacts are of gallium or gallium alloys.

An important advantage is obtained in both uses, because of the lowvapor pressure of gallium. When using a solid cooperating contact, wherethe iluid Contact material is open to the air, we obtain the advantagethat gallium does not vaporize at all at ordinary room temperatures, sothat dangers as to bodily health will be avoided. The contact resistancebetween gallium and a solid contact member may be reduced to a verysmall value and this is even true when the contact is covered with alayer of grease, which may easily happen because of handling.

With regard to the second object of this invention, and particularlywhere both conta/ct members are uid, gallium has the great advantagethat great amounts of energy can be interrupted because of the very lowvapor pressure, so there is a minimized danger that an arc will bestarted and will continue when large amounts of energy are interrupted.

The fact that gallium changes from the solid to the iiuid form only whenit reaches a temperature of 30 C. causes no substantial drawback becauseit is easy to provide an auxiliary heating means to maintain the galliumat a temperature above its solidiiication point. As a source of electricenergy is always available when gallium is used for circuit breakercontacts, it is desirable to `utilize electric heaters, as they arecommercially eilicient and may also be easily adapted to the device.

An illustration of the principles of my invention will be found in thedrawing in which Fig. 1 shows a separable contact or terminal Fig. 2shows a switch in which the separable contacts are both of gallium andFig. 3 shows a switch in which one separable contact is of gallium andthe other of a solid conductor.

(Cl. 20o-152) Referring in detail to Fig. 1 a terminal post 1 is adaptedto be supported in an insulating panel 2 or the like by means of athreadedy stud 3, to which a cable terminal 4 may be bolted, welded orotherwise connected. At the top of post 1 is a 60 cup 5 containing somemetallic gallium or gallium alloy 6. A cooporating terminal 7 to which asecond cable 8 is soldered, welded or otherwise conected is pressedfirmly down intol contact with the gallium 6 by a threaded bolt and nut9 65 or other well known pressure exerting means. The post 1 may beheated above the melting point of the gallium if desired veither whenthe contact 7 is iirst bolted home, or alternatively may be maintainedat such temperature by auxiliary heating means such as an electricheater 11.

Referring to Fig. 2 a container 21 preferably, Vacuum tight, ofinsulating material has two inleading conductors 22, 23 each of whichdips into a quantity of gallium or gallium alloy, the conductor 23dipping well down into a well 25 in the container wall. An electricheater 26 and heat insulation 27 may be provided if desired. Thecontainer 21 may be maintained at high vacuum, say a ten millionth ofatmospheric pressure, or 50 may contain a gaseous atmosphere such asneon. An auxiliary chamber 27 formed with a well or depression 28 whichmay contain materials well known as getters such as alkali metals whichy absorb undesired gases may also be provided when desired. Theelectrical Contact is broken, when this arrangement is tiltedcounterclockwise by part of the gallium running into the end ofcontainer 21 adjacent conductor 22 and parting contact with a remnant ofthe gallium retained in 90 well 25.

The arrangement of Fig. 3 differs in principle from that of Fig. 2 onlyin that the electrical contact is broken between the gallium and a solidconductor 31 and it needs no separate detailed deg5 scription. It may beprovided with a heater and auxiliary chamber similar to 27 of Fig. 2 ifdesired.

When using a gallium circuit breaker of the kind in which the gallium isseparated to `interrupt the circuit, any insulating material may be usedfor the tank or casing, which will not be affected by the gallium underthe operating conditions existing in the breaker, e. g. borosilicate,

glass or quartz glass. These casings may either be evacuated in theusual manner and maintained at a high vacuum, or they may be i'llledwith one or more suitable gases which are neutral, such as a pure noblegas, argon, helium, or a mixture such as neon and helium. no

As the character of the contact with or by gallium is deleteriouslyaiected by coatings of oxide thereon, materials are introduced,preferably into an auxiliary container communicating with the maincasing containing the gallium, which are capable of combining withhydrogen, oxygen and other substances which might affect the contactresistance and increase the same, such materials including the alkali oralkali earth metals. It is also desirable to use the present highvacuummethods of removing the water coating from the container in which thecontacts are located; and it is further advisable to degasify thegallium or the gallium alloy in a high vacuum. The heating of thegallium contact material can also be dispensed with if an alloy is usedwhose melting point is lower than that of pure gallium. Such an alloycan be made by the use of aluminum for the alloying means.

For the solid cooperating contact member, high melting point metalswhich do not react with gallium, such as tungsten, molybdenum, tantalum,iron, nickel or alloys of these metals with each other lor with othersubstances, may be employed, and in order to maintain the desired highquality of the contact it is desirable to degasify these metals oralloys as completely as possible in a high vacuum, even in cases to meltthem in a vacuum and to permit them to solidify therein.

I claim as my invention:

1. In an electric circuit, a pair of separable contact members at leastone of which consists of gallium.

2. In an electric circuit, a pair of separable contact members at leastone of which contains gallium in the form of a gallium alloy.

3. Contact device according to claim 1, characterized in that onecontact member consists oi gallium and the other contact member consistsof a solid conducting material, preferably o! a high melting point metalwhich does not react with gallium, such as tungsten, molybdenum,tantalum, iron, nickel, or of their alloys with each other or with othersubstances.

4. Contact device according to claim 1 characterized in that saidcontacts are contained in borosilicate or quartz affect the character ofthe contact, e. g. alkali orI earth alkali metals, located in anauxiliary container communicating with the main container.

7. Contact device according to claim 1, characterized by the use ofmetallic contacts including gallium or gallium alloys which have beendegasied or reduced in high vacuum.

8. Contacts according to claim l, characterized by the use of properelectric heating means providing such an amount of heat for the galliumcontact member that the temperature of the contact will be maintainedabove 30 centigrade even under the lowest temperatures occurring inoperation.

9. Contact device according to claim 1, characterized by the use of agallium alloy Whose melting point is lower than that of pure gallium.

RICHARD SWINNE.

